This invention relates to chemical compositions which are metal salts of carboxylic acids herein described, that are soluble in hydrocarbon oils and are used to inactivate odor producing sulfhydryl compounds that are present in hydrocarbon oils or other organic materials, in mixtures containing these materials, and in compositions which come in contact with these materials.
BACKGROUND OF THE INVENTION
The presence of sulfhydryl compounds and particularly hydrogen sulfide in hydrocarbon oils and other organic materials, mixtures containing these materials, and aqueous, solid, or gaseous phases in contact with these materials is an important environmental and safety and health problem in a broad range of industries. Sulfhydryl compounds include H2S, organo sulfur compounds containing Sxe2x80x94H groups also called mercaptans, thiol carboxylic acids RC(O)SH, dithio acids RC(S)SH, and related compounds.
In the petroleum industry the H2S content of crude oils in many areas of the world is high enough to present environmental and safety hazards. Hydrogen sulfide is flammable, corrosive, highly toxic, and a strong irritant. It is produced by sulfate reducing bacteria in the anaerobic environments encountered in oil wells and is highly soluble in the crude oil, from which it is released when the oil is removed from the well. H2S may be transferred to oil based drilling fluids when the fluids come in contact with H2S rich environments, where it becomes a hazard as the drilling fluid is recirculated from the well to the surface.
Sulfhydryl compounds and their resultant odors are also a problem in metal working environments. Sulfate reducing bacteria are often present in the recirculating metal working fluid systems, and though the bacteria can usually be controlled by the use of biocidal compositions, these biocide systems are difficult to control and monitor, and can occasionally fail, resulting in the offensive and hazardous formation of H2S in the fluids. The biocides cannot remove H2S after it has formed and thus a back-up means for removing it is desirable. Also, sulfurized oils are widely used in this industry because the sulfur from these compositions reacts with iron and provides lubricating benefits. These oils release undesirable volatile hydrogen sulfide and mercaptan compounds which are not essential to the effectiveness of the lubricants, and it would be desirable to control odors from these compounds.
Sulfhydryl compounds and particularly H2S can present environmental and toxicity problems in gaseous phases in confined spaces, as for instance in sewage treatment facilities and particularly in shipping and storage containers for moisture sensitive materials that may emit H2S. It would be desirable to have a scavenger that could reduce the H2S concentrations in such locations. It would be particularly advantageous to have such a scavenger that is active in the absence of an aqueous phase.
A number of methods have been proposed to control hydrogen sulfide odors in hydrocarbon containing systems.
WO 98/02501 describes bisoxazolidines prepared by the reaction of 1, 2 or 1, 3 amino alcohols containing 3 to 7 carbon atoms with aldehydes containing 4 or fewer carbon atoms. These products can be made oil soluble by the correct choice of starting materials, and react with sulfhydryl compounds present in oil and gas streams to neutralize them. U.S. Pat. No. 5,347,004 describes reaction products of alkoxyalkylene amine, ammonia, and dialkylamines with aldehydes. These products are used to remove hydrogen sulfide from gas streams which are sparged into water solutions of the products. U.S. Pat. No. 6,024,866 describes reaction products of an alkylenepolyamine with formaldehyde which can be made either water or hydrocarbon soluble.
Zinc and iron compounds have been used for this application. U.S. Pat. No. 3,928,211 describes the use of inorganic zinc salts preferably dispersed into aqueous or nonaqueous oil well drilling fluids with an organic dispersant such as lignin containing materials. U.S. Pat. No. 4,147,212 describes a water soluble zinc ammonium carbonate complex used to remove hydrogen sulfide from oils and gases by contact with aqueous solutions of the complex. U.S. Pat. No. 5,792,438 describes the activation of iron oxide by copper oxide to increase the rate of reaction of iron oxide and sulfur compounds. U.S. Pat. No. 4,756,836 discloses the use of chelated iron to oxidize H2S to elemental sulfur. The iron chelate is oxygen regenerated and recycled.
Metal salts of carboxylic acids and methods for their production are known. U.S. Pat. No. 2,584,041 describes a method to produce oil soluble metal salts of carboxylic acids in organic solvents by a hydrous two-phase fusion process. U.S. Pat. No. 2,890,232 describes a method for preparing polyvalent metal soaps of higher aliphatic monocarboxylic acids by a slurry process in which the acids are heated and slurried with the metal oxides in the presence of water. U.S. Pat. No. 5,443,698 describes an electrolytic method for synthesizing metal carboxylates.
It is an object of this invention to provide compositions which effectively remove odors caused by sulfhydryl compounds from crude oils, metal working fluids, and other organic materials; and liquid, solid or gaseous phases in contact with these materials.
It is a further object to provide compositions which are readily soluble in the hydrocarbon oils encountered in environments such as oil wells and metal working fluids.
It is a further object to provide compositions which do not contain aldehydes or toxic metals.
It is a further object to provide a method for the removal of odor producing sulfhydryl compounds from crude oils, metal working fluids, and other organic materials; and liquid, solid or gaseous phases in contact with these materials.
The oil soluble sulfhydryl compound scavengers of this invention are metal carboxylates or soaps of the formula:
Mn+Rxe2x80x94CO2xe2x88x92)x(OH)nxe2x88x92x
wherein M is a metal ion whose sulfide salt is less than 0.01% soluble in water, n is 2 or 3, x is an integer from 1 to n, and R a hydrocarbyl radical containing from about 4 to about 19 carbon atoms, and mixtures of these compositions.
A method is also provided to control odors produced by sulfhydryl compounds wherein the compositions containing the said sulfhydryl compounds are contacted with the metal carboxylates described above.
The metal carboxylate salts of this invention can be prepared by known methods starting from carboxylic acids or their water soluble salts, and metals, metal oxides or metal salts.
The carboxylic acids used to prepare the compositions of this invention contain from about 5 to about 20 carbon atoms, and are chosen from those which form oil soluble salts with the metal ions of this invention. Preferred are acids which form metal salts that are liquid below about 100xc2x0 C., and most preferred are those which form metal salts that have pour points below about 25xc2x0 C. As a rule the formation of low melting salts requires that the carboxylic acids used in the synthesis have highly branched structures. Also preferred are lower molecular weight acids because they are more efficient on a weight basis for the intended application.
Examples of Suitable Acids Include:
1. Neoacids. These are synthesized by reacting under high pressure and at elevated temperature a branched olefin and high-purity carbon monoxide in the presence of an acidic catalyst and water. The resulting acids have a tertiary carbon adjacent to the carboxyl group and are mixtures of isomers of the structure: 
wherein R1, R2, and R3 are each alkyl radicals containing 1 to about 16 carbon atoms, with the total number of carbon atoms contained in R1, R2, and R3 being from about 3 to about 18.
Neoacids with 7 or more carbon atoms are mixtures of isomers. For example, the typical isomer distribution of neodecanoic acid is: R1 and R2 are methyl, R3 is C6, 31%; R1 is methyl, R2 and R3 are C2 to C5, 67%; R1 is C2, R2 and R3 are C2 or C3, 2%.
Readily available and suitable neoacids include neopentanoic acid, neoheptanoic acid, neooctanoic acid, neononanoic acid, neodecanoic acid, and neotridecanoic acid. Neoacids with up to an average of about 20 carbon atoms are also available as mixtures of chain lengths and isomers, and are also suitable, as are mixtures of any of the described neoacids in any proportions. Neodecanoic acid is readily available and forms low viscosity salts and is preferred.
2. Naphthenic acids. As used herein, this term means the generic designation of monocarboxylic acids of naphthene hydrocarbons, present in crude mineral oils, which acids have the formula R4(CH2)nCOOH, wherein R4 is a cyclic nucleus composed of one or more rings, i.e., cyclohexane, cyclopentane, and their alkylated cyclic nuclei in general; and n is an integer from 1 to about 14. The carboxylic acid group combines with the ring nucleus (R4) through methylene (xe2x80x94CH2xe2x80x94)n groups. The simplest and typical acid, when n=1 is cyclopentane acetic acid.
Commercial naphthenic acids suitable in this invention are mixtures of inseparable organic acids having from 7 to about 20 carbon atoms and a cyclic nucleus. Accordingly, the naphthenic acid is used as a mixture of substances having the formula given above, and may also contain a minor amount of upsaponifiable material, which is unspecified but usually hydrocarbon in nature. Preferred naphthenic acids have equivalent weights per carboxylic acid functionality of less than about 300, and more preferred naphthenic acids less than about 250.
3. Isoacids of the structure:
R5xe2x80x94CH2xe2x80x94COOH
wherein R5 is a hydrocarbyl group containing from about 3 to about 17 carbon atoms including at least one substituted methyl group on other than the terminal carbon atom. Commercially available isoacids are usually mixtures of isomers which differ in the number and position of the methyl substitutions. Suitable available isoacids include isopentanoic acid, isoheptanoic acid, isooctanoic acid, isononanoic acid, isodecanoic acid, and isotridecanoic acid.
4. Guerbet acids, obtained from Guerbet alcohols, of the structure: 
wherein R6 is a hydrocarbyl group containing from about 2 to about 8 carbon atoms, and R7 is a hydrocarbyl group containing from about 4 to about 10 carbon atoms, and R6 always contains exactly 2 carbon atoms less than R7 Available and suitable Guerbet acids include 2-ethylhexanoic acid, 2-butyloctanoic acid, 2-hexyldecanoic acid, and 2-octyldodecanoic acid.
5. Unsaturated acids such as oleic acid, and tall oil fatty acid.
Saturated straight chain fatty acids are less preferred because the metal salts of these acids usually have melting points above 100xc2x0 C. Zinc laurate melts at 128xc2x0 C and zinc stearate melts at 130xc2x0 C.
The metal ions used to prepare the carboxylate salts of this invention are chosen from those which form water insoluble or sparingly soluble sulfide salts. Preferably the metal sulfides have solubility in water less than 0.01 g/100 cm3. The metal sulfides shown in the following table all are adequately insoluble. The preferred metals have low toxicity in the environment; thus highly toxic metals such as Hg, Pb, and Cd are less preferred. Because these compositions may in some applications be in contact with aqueous phases and at the same time with equipment such as drilling casings constructed of iron is it also preferred that the metals be more electronegative than iron so that they do not electrodeposit on the iron surfaces and cause corrosion of the iron. Because they are relatively nontoxic in the environment and do not cause iron corrosion, Zn, Fe, and Mn are the preferred metal ions. The Zn salts are readily synsthesized, are low in color, and are usually less viscous than other salts, and are most preferred.
The metal carboxylates of this invention are soluble in hydrocarbon oils. For the purposes of this invention hydrocarbon oils are described as compositions which are substantially free of elements other than carbon and hydrogen, and have flash points greater than about 90xc2x0 C. measured by the Tagg Closed Cup method. They may contain unsaturation, aromatic groups, and branched and cyclic structures.
The oil soluble metal carboxylates are in general known compositions and can be synthesized by methods described in the art. Suitable methods include:
1. Reaction of the metal oxide or hydroxide with the carboxylic acid. This method is described in U.S. Pat. No. 2,890,232, which is incorporated herein by reference. We have found that reactions of ZnO with the carboxylic acids of this invention do not require the addition of excess water to obtain an adequately fast reaction, if the reaction mix is heated at a rate such that the water released in the reaction is not driven off before the reaction is completed. An excess of ZnO beyond the amount necessary to exactly neutralize the carboxylic acid can be added up to about a two fold excess.
2. Double decomposition reactions using water soluble metal salts and water soluble carboxylate salts. In this method water solutions of the reactants are mixed and the oil soluble salt separates from a water solution of the salt of the counterions. This method usually requires the addition of a solvent to decrease the viscosity of the oil soluble salt, and the aqueous salt solution byproduct may create a disposal problem.
3. Direct reaction of the carboxylic acid and the metal in the presence of water. This method is described in U.S. Pat. No. 2,584,041, incorporated herein by reference. This method requires the addition of solvent and water, and the reaction proceeds rather slowly.
This invention also encompasses a method for controlling odors produced by sulfhydryl compounds wherein the compositions containing the said sulfhydryl compounds are contacted with the metal salts of this invention.
For applications in which the odor producing sulfhydryl compounds are dissolved in hydrocarbon or other organic materials, such as H2S containing crude oils, nonaqueous metal working fluids, and the like, the metal carboxylate scavenger compounds of this invention can be added directly to the materials. It may be desirable to dilute the metal carboxylates with a diluant to decrease the viscosity and allow for more efficient mixing of the scavenger throughout the odorous material. Suitable diluants are low viscosity organic solvents and oils that are compatible with both the scavenger and the substrate. Low viscosity mineral oils are highly suitable. The application level required is at least enough to react with the sulfhydryl materials present. When zinc neodecanoate is used to remove H2S, approximately 12.5 parts by weight of scavenger is required for each part of H2S present.
For applications in water based metal working fluids, the metal carboxylate scavenger compositions of this invention can be added directly to aqueous system with good agitation. Preferably they can be dispersed or dissolved into a portion of the base fluid, which typically comprises a sulfated hydrocarbon material, and then added to the water based fluid.
For removing odors caused by sulfhydryl compounds from gaseous phases, the scavenger compositions of this invention can be contacted with the gaseous materials by a number of means. The effectiveness of the compositions will depend on the surface area of the scavenger composition in contact with the gaseous phase. In some applications, the scavengers can be sprayed, either by themselves or dissolved in an oil or solvent, or emulsified into water, as fine particle droplets into the contaminated volume. In other applications, particularly in closed spaces, the scavenger compositions can be mixed with a high surface area powder such as precipitated silica, diatomaceous earth, and the like, to form a powdered composition which can be exposed to the atmosphere in the closed space. In other applications the scavenger compositions can be distributed onto the fibers of highly absorbent low density fiber mats, which are then exposed to the contaminated gaseous compostions.